1. Field of the Invention
The invention concerns a drum rotor for an axial flow turbomachine in which the blades are fastened by means of their roots in rows in circumferential blade grooves with support indentations at the side.
2. Discussion of Background
Such blade fastening arrangements are usually found in compressor and turbine rotors. During each rotation of the rotor, the circumferential blade grooves alter their axial dimension due to rotor bending. The change in dimension takes place with an amplitude which depends on the particular design. If the amplitude exceeds a certain magnitude, damage due to frictional fatigue can occur on the blade roots or on the turned recesses on the rotor. The corresponding parts of the first turbomachine stage in multi-stage machines are particularly endangered because there is no mutual relief provided by adjacent blade grooves. In consequence, noticeably larger relative displacement amplitudes occur in this first blade groove compared with those in the subsequent blade grooves. This matter is explained in FIGS. 2 and 3, which will be described later.
In addition, strong asymmetrical displacements occur in the first blade groove during changes in temperature, on starting or in the case of load changes or of operational fluctuations. These displacements lead to excessive local surface pressures in the blade root support indentations of the first rotor row.